<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>背景图</title>
        <style>
            *{
                margin: 0;
                padding: 0;
            }
            div,#w2{
                width: 450px;
                height: 450px;
                float: left;
                border: 1px solid red;
            }
            li{
                  width: 100px;
                  height: 100px;
                  background: pink;
                  list-style: none;
                  float: left;
              }
            ul li:nth-child(4){
                height: 200px;
            }
            #w2 li:nth-child(2){
                height: 200px;
            }
        </style>
    </head>
    <body>
        <!--浮动特殊情况一-->
        <div>
            <ul>
                <li>1</li>
                <li>2</li>
                <li>3</li>
                <li>4</li>
                <li>5</li>
            </ul>
        </div>
        <div id="w2">
            <ol>
                <li>1</li>
                <li>2</li>
                <li>3</li>
                <li>4</li>
                <li>5</li>
            </ol>
        </div>
    </body>
</html>